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Help needed with very simple model--diffusion across a boundary
Posted 25.06.2012, 10:20 GMT-4 1 Reply
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Hi,
I'm very new to comsol and am trying to start off with a simple problem. I have two squares touching on one side, and I want to model diffusion of two diluted species, where each square starts with 100% of one of the species and then it diffuses as if there's no boundary between them. I would like to model the concentration of the two species as a function of time. I know how to create the two squares and set them next to each other, but I don't know what to set the boundary between them as, whether I should form the two squares into a union or assembly, how to define it so that it has 100% of one species in one square and 100% of the other species in the other square. When I try to set an initial values condition, it won't allow me to remove either domain from it--everything is grayed out. Any help would be appreciated; thank you!!
I'm very new to comsol and am trying to start off with a simple problem. I have two squares touching on one side, and I want to model diffusion of two diluted species, where each square starts with 100% of one of the species and then it diffuses as if there's no boundary between them. I would like to model the concentration of the two species as a function of time. I know how to create the two squares and set them next to each other, but I don't know what to set the boundary between them as, whether I should form the two squares into a union or assembly, how to define it so that it has 100% of one species in one square and 100% of the other species in the other square. When I try to set an initial values condition, it won't allow me to remove either domain from it--everything is grayed out. Any help would be appreciated; thank you!!
1 Reply Last Post 25.06.2012, 15:32 GMT-4
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Posted:
1 decade ago
Hi
first of all if you draw your 2 squares adjacent with a common or overlapping boundary, then use the default Union Finish mode, your boundary between the two domains will have the default continuity condition that is for 2 objects in contact exchanging without any resistance (as if the boundary is not there.
To define 1 initial conditions, define c1=100% on the default Initial condition (valid for BOTH domains), then add a new domain initial value node (right-click the main physics), select the second domain, and set c2 = 100%. If you go back to the first initial condition you will notice now that it says domain 2 (overridden) because you have added a node further down that over-rides the definition of the previous node. COMSOL always adds a few Default nodes, these you cannot deleted, but you can override them partially or totally
--
Good luck
Ivar
first of all if you draw your 2 squares adjacent with a common or overlapping boundary, then use the default Union Finish mode, your boundary between the two domains will have the default continuity condition that is for 2 objects in contact exchanging without any resistance (as if the boundary is not there.
To define 1 initial conditions, define c1=100% on the default Initial condition (valid for BOTH domains), then add a new domain initial value node (right-click the main physics), select the second domain, and set c2 = 100%. If you go back to the first initial condition you will notice now that it says domain 2 (overridden) because you have added a node further down that over-rides the definition of the previous node. COMSOL always adds a few Default nodes, these you cannot deleted, but you can override them partially or totally
--
Good luck
Ivar